The female equivalent to "sloppy seconds", floppy seconds occurs when a woman receives an inadequate dose of dongage due to the fact that the male in question has recently enacted in coitus with another woman, thus rendering his manhood "floppy".

"Well, I already banged your sister, but if you don't mind floppy seconds..."
or
"Man, that Kate Hudson chick sure does like floppy seconds!"

Simular to the term sloppy seconds, however referring to the male who has recently had sex with a women, and promptly after attempting to have sex with another women however he is unable to immediately generate an erection.

Dude last light I took these two girls home, could only handle one at a time so had to give one of them floppy seconds